These are also known as practice contractions, and while they can definitely get your attention, they don’t cause your cervix to dilate or cause you to go into labor.
Braxton Hicks contractions often start showing up in the second trimester. It’s your uterus’s way of “practicing” or getting ready for the big day. However, these are not true labor contractions. They are not regular or painfully strong. Many women will notice them as a tightening or mild cramp. And they often appear during certain times: when you are dehydrated, after exercise or sex, or when your bladder is very full (such as in the middle of the night).
If you notice strong, regular contractions that are timeable, these may be real contractions and could be a sign of preterm labor. Be sure to give your doctor or midwife a call, so they can make sure nothing concerning is going on.